This invention pertains to the art of valves and, more particularly, to shutoff valves.
The invention is particularly applicable to a fluid pressure actuated shutoff valve and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may advantageously be employed in other valve and related environments.
Shutoff valves conventionally employ a construction in which a valve member is selectively movable axially toward and away from a stationary valve seat to selectively control fluid flow through a valve. Actuation of the valve member may be manual or, alternatively, may be effected by power means. System fluid pressures and economics dictate whether manual or power actuated shutoff valves are used.
Typically, a soft or yielding material is provided on the end of the valve stem for sealing cooperation with a metal valve seat. Contact between the resilient material and metal ensures a tight sealing fit between the coacting members. In addition, use of a resilient material can withstand repeated valve openings and closings, even though the material is subjected to gradual wearing or deterioration. The resilient material causes little, if any, galling action on the valve seat, so continued sealing is readily achieved. In addition, a resilient seal can adapt to the presence of particulate matter in the system fluid while maintaining a tight seal.
Leakage around the valve tip seal is of primary concern with shutoff valves and is normally encountered after extended valve use. One type of prior art valve employs a stem tip in which a soft sealing material is bonded to the outer end of the stem. Repeated opening and closing of the valve exerts a spring force which causes the bond and seal to break down. Another prior art shutoff valve construction positions a seal ring in an annular groove formed in the end of the valve member. Nibbling or chipping and blow out of the seal ring are problems which are encountered as system fluid pressures increase.
In view of the foregoing difficulties, it has been considered desirable to develop a new stem tip arrangement for providing sealing action capable of extended use without encountering failure, blow out, and the like. The invention of the subject application is believed to successfully and economically meet these needs and others.